The invention relates to a fresh gas supply device for an internal combustion engine. The invention also relates to a method for operating the fresh gas supply device.
Internal combustion engines, for example diesel engines, are often equipped with exhaust gas turbochargers. FIG. 1 illustrates an internal combustion engine 1, the exhaust gas line 14 of which is connected to an exhaust gas turbine 4 of an exhaust gas turbocharger 2. This exhaust gas turbine 4 drives a compressor 3 of the exhaust gas turbocharger 2. The compressor 3 compresses intake air from a fresh gas inlet 8 and consequently increases an intake pressure in an intake line 13 of the internal combustion engine 1. As a result, for example, an acceleration behavior of the vehicle having the internal combustion engine 1 is improved and a reduction in fuel consumption is achieved.
However, the exhaust gas turbocharger 2 is not capable of conveying sufficient air, and therefore of generating sufficient intake pressure, in every operating state of the internal combustion engine 1. For example, piston engines, such as diesel engines, with an exhaust gas turbocharger 2 have, for example, an operating state during acceleration which is designated as “turbo lag”. In this case, when the accelerator pedal is depressed, the internal combustion engine 1 reacts with an increase in rotational speed only after a specific delay time in which no exhaust gas energy, that is to say also no sufficient exhaust gas pressure, for driving the exhaust gas turbocharger 2 and therefore no compressed intake air with a corresponding intake pressure are available. To bridge this “turbo lag”, proposals for a solution have been made in which compressed air is introduced, for example from a compressed air reservoir 6 fed by an air compressor 7, into the intake line 13 of the internal combustion engine 1 in a controlled manner, in order, when the internal combustion engine 1 has an increased intake air demand, to cover this. This takes place by way of a fresh gas supply device 20, which is arranged between the compressor 3 of the turbocharger 2 (or a charge air cooler 5 following in a flow direction) and the intake line 13.
Such a fresh gas supply device 20 is illustrated diagrammatically in FIGS. 2 and 3 in sectional views in two operating states or positions. The fresh gas supply device 20 has a housing body 21 and is connected by way of a charge air inlet 9 to the charge air cooler 5, by way of an outlet 10 to the intake line 13, and by way of a compressed air inlet 11, via a compressed air line 12, to the compressed air reservoir 6. Located between the charge air inlet 9 and the outlet 10, between an inlet portion 16 and an outlet portion 18, is a valve portion 17 in which a flap valve 23 for closing and opening the valve portion 17 is arranged. The flap valve 23 is preferably designed to be pivotable about a flap axis of rotation 24. The compressed air line 12 with the compressed air inlet 11 communicates via an injection port 19 with the outlet portion 18. In this case, the compressed air line 12 is arranged such that a compressed air flow 30 is directed toward the outlet 10 of the outlet portion 18.
FIG. 2 shows the fresh air supply device 20 in a position for additional air or compressed air. In this case, the flap valve 23 is pivoted about the flap axis of rotation 24 such that it closes the valve portion 17 and therefore the connection of the inlet portion 16 to the outlet portion 18. In this closing position, the flap valve 23 bears with its outer margin against a stop portion 25 of the housing body 21 and closes the valve portion 17.
FIG. 3 illustrates the fresh air supply device 20 in a position for charge air. The flap valve 23 is pivoted counterclockwise about the flap axis of rotation 24 and has opened the valve portion 17. The charge air flow 28 can flow through the valve portion 17 into the outlet portion 18 and into the outlet 10 in order to form an intake flow 29, which flows into the intake line 13 of the internal combustion engine 1. The compressed air flow 30 is absent in this case, the compressed air line 12 being closed, for example, by means of a valve.
In one version, the flap valve 23 pivots into its closing position (FIG. 2) when the pressure in the flow direction of an intake flow 29 into the intake line 13 (not shown here) in the outlet portion 18 is higher than the pressure of a charge air flow 28 in the inlet portion 16. This takes place in that, when torque is required for the internal combustion engine 1, the compressed air line 12 is acted upon in a way not shown by the compressed air flow 30 for the additional air to be injected. For this purpose, however, the corresponding pressure first has to build up, and therefore losses may occur. This compressed air injection can take place, in practice, only when no compressed air losses occur on account of the compressed air available to a limited extent in a vehicle. For this reason, the flap valve 23 prevents a backflow of the compressed air flow 30 into an opposite charge air flow 28 into the inlet portion 16. The flap valve 23 is coupled to an adjusting device 22, which is normally formed by a restoring spring which, in the absence of the pressure of the charge air flow 28, pivots the flap valve 23 into the closed position shown in FIG. 2, that is to say the position for compressed air. In the case of such an adjusting device 22 with a spring, that is to say in the case of what is known as a spring non-return valve, the closing times may become too long. Too much compressed air may therefore flow into the inlet portion 16 and in the direction of the charge air cooler 5 or compressor 3.
In another version of a device for the fresh air supply of a turbocharged piston internal combustion engine and a method for the operation thereof which is described in the application WO 2006/089779 A1, the flap valve 23 is adjusted by the adjusting device 22, for example designed as a variable displacement motor. Furthermore, the compressed air inlet 11 is connected to the compressed air reservoir 6 by means of the outlet 10 via a quantity regulating device (not shown), for example a valve. A control device, not shown, serves for controlling the quantity regulating device and the variable displacement motor. In the event of a torque requirement during “kick down”, the quantity regulating device feeds a compressed air flow 30 through the compressed air inlet 11 to the outlet 10. The flap valve 23 is previously closed by the adjusting device 22, so that the compressed air flow 30 does not flow via the charge air inlet 9 into the compressor 3 of the exhaust gas turbocharger 2 opposite to the intake direction or charge air flow 28, but instead, via the outlet 10, into the intake line 13. When the feed of compressed air is ended, this flap valve 23 is opened again and the quantity regulating device is closed. At this time point, the pressure of the charge air flow 28 in the inlet portion 16 through the compressor 3 of the exhaust gas turbocharger 2 is again sufficient.
A flap valve 23 with a restoring spring as an adjusting device 22 may entail a pressure loss and therefore also a loss of time, with accompanying energy consumption. On the other hand, an electrical adjusting device 22, for example a servomotor with a position transmitter and associated activation, results in a larger number of components and a corresponding cost outlay.
The object of the present invention, therefore, is to provide an improved fresh gas supply device. A further object is to specify a corresponding method for operating a fresh gas supply device.
According to one aspect of the invention, a fresh gas supply device is provided for an internal combustion engine having an exhaust gas turbocharger. The fresh gas supply device includes: a charge air inlet for the inlet of a compressed charge air flow out of the exhaust gas turbocharger; an outlet which is connected to the charge air inlet via a valve portion, the valve portion being closeable in a closing position by at least one valve, preferably a flap valve pivotable about a flap axis of rotation; an adjusting device which is coupled to the at least one valve, in particular to the flap valve, for adjusting the latter into the closing position; and a compressed air inlet for the inlet of compressed air into the outlet, the compressed air inlet being arranged such that the compressed air is oriented in a compressed air flow onto the at least one valve, in particular the flap valve, in the direction toward the valve portion.
According to another aspect of the invention, a method is provided for operating a fresh gas supply device for an internal combustion engine having an exhaust gas turbocharger, the fresh gas supply device including: a charge air inlet for the inlet of a compressed charge air flow out of the exhaust gas turbocharger; an outlet which is connected to the charge air inlet via a valve portion, the valve portion being closeable in a closing position by at least one flap valve preferably pivotable about a flap axis of rotation; an adjusting device which is coupled to the at least one flap valve; and a compressed air inlet for the inlet of compressed air into the outlet. The method includes the acts of: determining a torque requirement of the internal combustion engine and monitoring the charge air flow; injecting compressed air into the fresh gas supply device in a compressed air flow oriented onto the at least one flap valve opposite to the direction of the charge air flow, wherein the adjusting device adjusts the at least one flap valve for closing the valve portion, and the compressed air flow assists a closing movement of the at least one flap valve; and ending the injection of compressed air on the basis of the monitoring of the charge air flow.
An advantageous aspect of the invention is to direct the compressed air to be injected toward the valve, in particular the at least one flap valve, opposite to the charge air flow or to an intake flow.
In this case, it is preferably possible that the at least one flap valve is designed as a spring non-return flap valve, the adjusting device being designed as a restoring spring. This simple version can advantageously be implemented with a small number of components.
The at least one flap valve is coupled eccentrically to the flap axis of rotation, and because of this the flows and pressure conditions acting upon the flap valve result in a pivoting movement assisted by the flows and pressure conditions.
For this purpose, it is advantageous that the at least one flap valve has a first onflow portion for cooperation with the charge air flow and a second onflow portion for cooperation with the compressed air flow.
In this case, it is preferable that the compressed air flow is oriented onto the second onflow portion of the at least one flap valve for adjusting the latter into the closing position. This affords the advantage of a marked reduction in the closing time of the simple mechanical spring non-return valve, since the system pressure in compressed air installations in a vehicle amounts, for example, to 8 bar, whereas the charge air pressure when an internal combustion engine is under low load and requires torque is markedly lower than 1 bar. On account of this short closing time, compressed air losses are reduced. A reaction time of the internal combustion engine to the torque requirement, that is to say acceleration of a vehicle which has this internal combustion engine, is thereby increased.
The compressed air inlet can be formed with an injection port which is shaped for steering the compressed air flow onto the second onflow portion of the at least one flap valve favorably in terms of flow. Thus, an installation space is reduced, since a compressed air line connection can consequently be adapted, in its position in the engine space of the vehicle, to the existing installation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.